1. Field of the Invention
The present invention relates to a gate valve which is capable of opening/closing, for example, a flow passage or a discharge passage, for example, for a pressure fluid or a gas.
2. Description of the Related Art
The operation has been hitherto performed, for example, for processing apparatuses for semiconductor wafers, liquid crystal substrates or the like, in which the semiconductor wafer, the liquid crystal substrate or the like is put in and out of various processing chambers through a passage. A gate valve for opening/closing the passage is provided for the passage.
Such a gate valve is arranged as follows, for example. as described in Japanese Patent No. 2613171. That is, a valve disk arrives at a position opposed to a valve seat in accordance with rectilinear motion of a valve rod which is displaceable in accordance with the driving action of a cylinder. After that, the valve disk is pressed against the valve seat, and it is seated thereon by the aid of the tilting motion of the valve rod. Accordingly, a passage, which is formed through a valve box, is closed.
That is, as shown in FIGS. 8 and 9, the gate valve 1 concerning the conventional technique comprises a valve box 3 which is formed with a passage 2 for putting in and out a workpiece, a valve disk 5 for closing the passage 2 by being seated on a valve seat 4 formed in the valve box 3, and a valve rod 6 which is connected to the valve disk 5 and which is provided to be tiltable and movable upwardly and downwardly.
A block 7 is connected to an upper portion of the valve rod 6. Pivotal shafts 11, which are displaceable along guide grooves 10 (see FIG. 10) formed on both side surfaces of cylinder tubes 9 of a pair of cylinders 8a, 8b respectively, are secured to both side surfaces of the block 7. The block 7 is provided to be tiltable and movable upwardly and downwardly in accordance with the guiding action of the guide grooves 10 with which the pivotal shafts 11 are engaged. Each of the cylinder tube 9, the block 7, and the pivotal shaft 11 is made of a metal material.
In other words, the block 7 makes rectilinear motion in the vertical direction integrally with a yoke 13 by the aid of tensile springs 12 in accordance with the guiding action of the guide grooves 10 with which the pivotal shafts 11 are engaged. The block 7 makes the tilting motion in the direction of the arrow A about support points of the pivotal shafts 11 which are supported by curved lower ends 10a (see FIG. 10) of the guide grooves 10. Therefore, the valve disk 5 is tilted in the direction of the arrow B about the support points of the pivotal shafts 11, and it is seated on the valve seat 4. Thus, the passage 2 is closed in an air-tight manner.
Reference numeral 14 indicates a plate-shaped cam having a rhombic cross section. The inclined plate-shaped cam 14 is displaced substantially horizontally, and thus the block 7 is tilted in the direction of the arrow A about the support points of the lower ends 10a of the guide grooves 10.
However, the gate valve 1 concerning the conventional technique described above is arranged such that the valve rod 6 makes the vertical movement and the tilting movement in accordance with the driving action of the pair of cylinders 8a, 8b, and the passage 2 is closed by the valve disk 5 which is connected to the valve rod 6. Therefore, in the case of the gate valve 1 concerning the conventional technique, it is feared that when the gate valve 1 is used for many years, the sealing performance for the passage 2 is deteriorated when the valve disk 5 is seated on the valve seat 4 to close the passage 2.